Emitter driver for noninvasive patient monitor

ABSTRACT

Embodiments of the present disclosure include an emitter driver configured to be capable of addressing substantially 2 N  nodes with N cable conductors configured to carry activation instructions from a processor. In an embodiment, an address controller outputs an activation instruction to a latch decoder configured to supply switch controls to activate particular LEDs of a light source.

REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent application No.12/875,062, filed Sep. 2, 2010, entitled “Emitter Driver for NoninvasivePatient Monitor,” which claims priority benefit under 35 U.S.C. §119 (e)from U.S. Provisional Application No. 61/239,741, filed Sep. 3, 2009,entitled “Emitter Driver for Noninvasive Patient Monitor;” thedisclosures of which are incorporated herein by reference.

The present disclosure is also related to the following applications.

App. No. Filing Date Title Attorney Docket 12/534,827 Aug. 3, 2009Multi-Stream Data CERCA.002A Collection System for Non invasiveMeasurement of Blood Constituents 12/534,812 Aug. 3, 2009 Multi-StreamCERCA.003A Sensor Front Ends for Noninvasive Measurement of BloodConstituents 12/534,823 Aug. 3, 2009 Multi-Stream CERCA.004A Sensor forNoninvasive Measurement of Blood Constituents 12/534,825 Aug. 3, 2009Multi-Stream CERCA.005A Emitter for Noninvasive Measurement of BloodConstituents 12/497,528 Jul. 2, 2009 Noise Shielding CERCA.006A for aNoninvasive Device 12/497,523 Jul. 2, 2009 Contoured ProtrusionCERCA.007A for Improving Spectroscopic Measurement of Blood Constituents29/323,409 Aug. 25, 2008 Patient Monitoring CERCA.009DA Sensor29/323,408 Aug. 25, 2008 Patient Monitor CERCA.010DA 12/497,506 Jul. 2,2009 Heat Sink for CERCA.011A Noninvasive Medical Sensor

Each of the foregoing is incorporated by reference herein in itsentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure generally relates to patient monitoring devicesand more specifically, embodiments of the present disclosure relate todriving light sources of patient monitoring devices to properlyirradiate tissue under observation.

2. Description of the Related Art

Spectroscopic patient monitoring systems including noninvasive patientmonitoring systems often energize a plurality of emission devices thatirradiate tissue under observation. In many systems, the emissiondevices irradiate the tissue at different wavelengths at differenttimes. The radiation is scattered and absorbed by the tissue such thatsome attenuated amount thereof emerges and is generally detected throughone or more photodetectors. The photodetectors output one or moresignals indicative of the intensity of the detected attenuated radiationand forward the signal to a patient monitor for processing.

In many systems, the patient monitor provides a drive signal configuredto activate each emission device at a different time over an activationcycle, thereby reducing a likelihood that a detector seeking a measureof attenuation in light of one wavelength will be effected by radiationfrom light of another wavelength.

For example, FIG. 1 illustrates a patient monitoring system 100including a patient monitor 102 communicating with a noninvasive opticalsensor 104 through cable 106. As shown in FIG. 1, the monitor 102displays calculated measurements derived at least in part fromprocessing an output signal from the sensor 104 indicative of lightattenuated by pulsing blood. As shown in FIG. 1, the monitor 102includes a driving circuit 108 configured to drive a sensor light source110, such as, for example, a two emitter light source configured to emitlight at different wavelengths. The emitters shown in FIG. 1 areconnected in parallel in a back-to-back configuration, although otherconfigurations and their drive circuitry requirements will berecognizable to an artisan from the disclosure herein, including, forexample, common anode, common cathode and the like.

In general, a processor of said monitor 102 controls various latchingmechanisms to activate one of voltage-to-current converters 112, 114 ata time. Once activated, the converters 112, 114 provide a currentthrough conductors of the cable 106 to an associated LED 116, 118 of thesensor 104. Thus, the processor may output appropriate latching signalsto the driving circuit 108 to precisely control a duty cycle and currentlevel for each of the LEDs 116, 118, and ensure that the LEDs 116, 118are activated one at a time. Examples of the driver circuitry of FIG. 1are disclosed in U.S. Pat. No. 6,157,850. The ‘850 patent disclosure isincorporated in its entirety by reference herein.

In contrast to the driving circuit 108 and light source 110 of FIG. 1,FIG. 2 illustrates a patient monitoring system 200 including a patientmonitor 202 communicating with a noninvasive optical sensor 204 througha cable 206. As shown in FIG. 2, the monitor 202 displays calculatedmeasurements derived at least in part from processing an output signalfrom the sensor 204 indicative of light attenuated by pulsing blood. Asshown in FIG. 2, the monitor 202 includes a driving circuit 208configured to drive a sensor light source 210, such as, a grid array ofLEDs capable of emitting light at different wavelengths of radiation.

In general, the driving circuit 208 includes a plurality of row drivers220 and a plurality of column drivers 222, the activation of aparticular row driver and a particular column driver corresponds to theactivation of one or a group of LEDs arranged at a corresponding node ina grid of rows 224 and columns 226. Such activation is controlledthrough one or more processors of said monitor 202 in order to preciselycontrol a duty cycle for each of the LEDs in the grid array, includingLEDs 216, 218. For example, row and column drivers 220, 222 functiontogether as switches to Vcc and current sinks, respectively, to activateLEDs and function as switches to ground and Vcc, respectively, todeactivate LEDs. This push-pull drive configuration advantageouslyprevents parasitic current flow, and thus, parasitic activation, indeactivated LEDs. In a particular embodiment, one row drive line 224 isswitched to Vcc at a time. Examples of the driver circuitry of FIG. 2are disclosed in U.S. pat. app. Pub. No. 2006/0241363. The ‘363 patentapplication's disclosure is incorporated by reference in its entiretyherein.

SUMMARY OF THE INVENTION

The foregoing LED driver circuits 108, 208 include some limitations. Thedriver circuit 108 uses a separate drive conductor for each LED of thelight source 110. Thus, in the system 100 of FIG. 1, the cable 106carries N drive currents over N conductors to drive N LEDs. As will berecognizable to an artisan from the disclosure herein, increasing anumber LEDs in the light source 110 to, for example, increase a numberof available wavelengths, corresponds to increasing a number ofconductors in the cable 106. Each increase of conductors carrying highemitter driver currents in the cable increases a likelihood ofinterference with other conductors of cable 106, such as thoseconductors communicating sensitive very low currents or voltages at highimpedance as output signals from the detectors of the sensor 104.Moreover, each increase of conductors increases cable size, cost,complexity, shielding, cable stiffness, and the like, thereby decreasingpatient comfort.

Driver circuit 208, including the row and column drivers 220, 222, is animprovement to the N-to-N driver circuit 108 of FIG. 1. For example, inthe system 200 of FIG. 2, the cable 206 carries N high emitter drivercurrents on N conductors. Half of the N conductors correspond to highcurrent row drive signals and half correspond to high current columndrive signals. These N conductors allow a processor to address and thusactivate specific nodes of a light source grid array of 2*N nodes.Similar to the N-to-N driver circuit 108, an artisan will recognize fromthe disclosure herein, that increasing a number LEDs in the light sourcegrid array 210 to, for example, increase a number of availablewavelengths, corresponds to increasing a number of conductors in thecable 206, thereby potentially increasing a likelihood of harmfulinterference in detector signals.

Based on at least the foregoing, when a need exists to increase a numberof different wavelength LEDs to accommodate more sophisticated signalprocessing of patient monitors, a need exists to find better solutionsfor driving light sources. Often, increasing available wavelengthscorresponds to seeking to measure physiological parameters that are moredifficult to distinguish from surrounding noise, including, for example,total hemoglobin monitors, glucose monitors, methemoglobin monitors,combinations of the same or the like, or corresponds to increasing thesensitivity in conventional pulse oximeters. However, simply increasinga number of high current conductors in a given cable 106, 206 can befraught with drawbacks including cable stiffness and crosstalk noise ondetector conductors.

Accordingly, embodiments of the present disclosure include a patientmonitoring system where a patient monitor employs addressing schemes toincrease a number of specifically selectable activation nodes of a lightsource. In an embodiment, an emitter driver is configured to addresssubstantially 2^(N) nodes, where N is a number cable conductorsconfigured to carry activation instructions from a processor. In anembodiment, an address controller outputs an activation instruction to alatch decoder configured to supply switch controls to logic devicesgoverning the activations of LEDs of a light source. In an embodiment, Ncable conductors can be used to uniquely address all or substantiallyall of 2^(N) LED nodes. In certain embodiments, the activationinstruction need not be a high current signal. For example, in some ofthe presently disclosed embodiments, a cable carries one or a few highcurrent emitter driver signals, which can be routed through logic andaddressing to a desired node of the light source. For example, in anembodiment where each LED of a light source can be driven with the sameor similar current, embodiments of the cable of the present disclosuremay carry a single high current conductor. In embodiments where LEDs ofa light source may use different currents to drive different types ofLEDs, such as, for example, light sources including superluminescent,laser or side emitting LEDs, along with more traditional LEDs,embodiments of the cable of the present disclosure may carry currentsappropriate for each type of LED over a plurality of high currentconductors. In many embodiments, however, the number of high currentconductors is dramatically reduced from that of the drivers disclosed inthe Background herein.

Embodiments of the present disclosure include a non-invasivephysiological sensor configured to output one or more signals indicativeof one or more physiological conditions of a patient being monitored.The sensor includes a plurality of light emitting sources configured fortransmitting optical radiation to a measurement site. The sensor alsoincludes one or more detectors configured to output said one or moresignals responsive to said optical radiation detected after attenuationby body tissue of said patient at said measurement site. The one or moresignals are indicative of said one or more physiological conditions ofsaid patient. The sensor also includes a plurality of switchesconfigured for selectively connecting one or more of the light emittingsources to one or more drive signals. Additionally, the sensor includesa decoder circuit configured for controlling the plurality of switches,wherein when said decoder circuit receives N inputs, said decodercircuit configured to selectively address up to 2^(N) unique locations.Each location includes one or more of said plurality of saidsemiconductor switches, wherein activation of one of said uniquelocations causes at least one of said light emitting sources to transmitsaid optical radiation to said measurement site.

Embodiments of the disclosure also include a cable communicating signalsbetween a patient monitor and a noninvasive optical sensor. The cablecomprises one or more signal lines configured to carry one or more drivesignals configured to activate one or more light sources of saidnoninvasive optical sensor. The cable also includes N address linescapable of selecting 2^(N) unique locations and configured toselectively connect up to about 2^(N) light emitting sources to ones ofsaid one or more drive signals. The connection activating said lightemitting sources to provide light to tissue of a patient wearing saidsensor and allowing one or more photodetectors to detect light from saidactivated sources after attenuation by tissue from said patient.

In still other embodiments, the disclosure includes a method toselectively drive light emitting sources in a noninvasive opticalphysiological sensor for monitoring parameters of a patient. The methodincludes attaching said sensor to a patient where said sensor includesat least one different semiconductor switch in series with each of thelight emitting sources. The method also including activating saidsemiconductor switches to connect associated light emitting sources to adrive signal. The light emitting source transmits optical radiation intoa measurement site of said patient, and said activation comprisesproviding N conductors to a decoder capable of controlling about 2^(N)of the semiconductor switches and configured to control up to about2^(N) of the semiconductor switches.

For purposes of summarizing the invention, certain aspects, advantagesand novel features of the invention have been described herein. Ofcourse, it is to be understood that not necessarily all such aspects,advantages or features will be embodied in any particular embodiment ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings and the associated descriptions are provided toillustrate embodiments of the present disclosure and do not limit thescope of the claims.

FIG. 1 illustrates a traditional patient monitoring system including apatient monitor communicating with a noninvasive optical sensor througha cable.

FIG. 2 illustrates another traditional patient monitoring systemincluding a patient monitor communicating with a noninvasive opticalsensor through a cable.

FIG. 3 illustrates a patient monitoring system according to embodimentsof the present disclosure.

FIG. 4 illustrates an exemplary block diagram of embodiments of thesystem of FIG. 3.

FIG. 5 illustrates an exemplary block diagram of embodiments of a driverof FIG. 4.

FIG. 6 illustrates an exemplary flowchart of a driving process accordingto embodiments of the present disclosure.

FIGS. 7A-7B illustrates exemplary block diagrams of alternativeembodiments of the driver of FIG. 4, where FIG. 7A illustrates a firstmethod of shorting unused LEDs and FIG. 7B illustrates a second methodof shorting unused LEDs.

FIG. 8 illustrates another exemplary block diagram of an embodiment ofthe driver of FIG. 4 configured to drive LEDs with different drivecurrent requirements.

FIG. 9 illustrates another exemplary block diagram of an embodiment ofthe driver of FIG. 4 configured to drive LEDs while avoiding a SYNCsignal through a patient cable.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Embodiments of the present disclosure include a patient monitoringsystem including a patient monitor having a driving circuitadvantageously capable of selectively activating 2^(N) LEDs of a lightsource using a decoder receiving an N signal address. In variousdisclosed embodiments, use of addressing and a decoder advantageouslyreduces a number of high current conductors in a cable communicatingsignals between the monitor and, for example, a noninvasive sensor. Forexample, in embodiments where a light source includes LEDs configured tobe driven by a single current, embodiments of the present disclosureprovide that the cable may carry a single high current conductor. Inother embodiments where the light source includes LEDs configured to bedriven at a first current and additional LEDs configured to be driven ata second current different from the first, embodiments of the presentdisclosure provide that the cable may carry the plurality of highcurrent conductors, one for each current required. While someembodiments shown herein require two currents, an artisan will recognizefrom the disclosure herein how to add additional currents when LEDconfigurations so require.

In the foregoing embodiments, the driver circuit advantageously includesuse of addressing and a decoder, the addressing information carried overconductors carrying lower, less interfering signals than those ofdriving currents. Accordingly, embodiments of the present disclosurereduce the potential of harmful crosstalk between high currentconductors carrying driver signals and low current conductors carrying,for example, sensitive detector signals. Moreover, cables associatedwith the present disclosure may advantageously require fewer largerheavily shielded driver conductors, and therefore, may be less costly toproduce, be less rigid or stiff and thus more ergonomic to a wearer of asensor.

In additional embodiments, each LED is shorted by a transistor that isconducting unless that particular LED is activated. Such shortingadvantageously reduces the likelihood of unwanted emissions by LEDsemitting unwanted wavelengths due to, for example, parasitic currents.Also, various embodiments include on/off timing hardware configured togovern the shorting transistors to improve timing of LED activations anddeactivations.

To facilitate a complete understanding of the invention, the remainderof the detailed description references to the drawings, wherein likereference numbers are referenced with like numerals throughout.

FIG. 3 illustrates a patient monitoring system 300 according toembodiments of the present disclosure. As shown in FIG. 3, the system300 includes a patient monitor 302, a noninvasive sensor 304communicating with the monitor 302 through a cable 306. The monitor 302drives a lights source including a plurality of emitters of the sensor304 to irradiate tissue of a wearer of the sensor 304. The sensor 304also includes one or more photodetectors that detect light attenuated bythe body tissue and output one or more signals indicative of thedetected light. The monitor 302 receives the one or more output signalsof the sensor 304, processes the signals and determines one or moremeasurement values of various physiological characteristics of thewearer. The monitor 302 includes a display 308 configured to providealphanumeric and/or graphical information to a caregiver. The monitor3021 also includes a plurality of user input devices 310 including forexample, a touch screen and one or more input keys. An artisan willrecognize from the disclosure herein that the input devices 310 couldcomprise one or a combination of control buttons, dials, knobs, or thelike, touch screen inputs, vocal commands, or the like.

Although disclosed as a portable handheld device, an artisan willrecognize from the disclosure herein that the monitor 302 may comprise adesktop or stationary monitor, may monitor some or many parameters, mayoutput information to legacy caregiver systems, may wirelesslycommunicated between sensors and monitors, between monitors and othermonitors, combinations of the same and the like.

FIG. 4 illustrates an exemplary block diagram 400 of embodiments of themonitor 302 of the system of FIG. 3. As shown in FIG. 4, the monitor 302may include one or more signal processors 402 communicating with a userinterface 404, network interface 406, memory and storage 410, sensorand/or cable memory 412, a front end interface 414 and driver circuitry416. In general, the processor 402 outputs control data to the drivercircuitry 416, which in turn selectively activates LEDs of a lightsource 418 to irradiate tissue, such as, for example a digit of thewearer. The tissue absorbs the irradiation and one or more detectors 420detect the attenuated light. The detectors output one or more signalsindicative of the attenuated light to the front end interface 414, whichfilters and pre-process the output signal. Signal processor 402 receivesthe processed and filtered output signal and determines measurementvalues for the one or more monitored parameters.

In various embodiments, the sensor 304 may include a tissue shaperconfigured to mechanically stabilize and/or control the shape of thedigit at the measurement site. In an embodiment, the tissue shaper mayadvantageously include a bump including a substantially cylindricalsurface. Additional embodiments of the tissue shaper are disclosed inU.S. patent application Ser. No. 12/534,827, filed on Aug. 3, 2009. Theteachings of the '827 application relating to the tissue shaper areincorporated by reference in its entirety herein. Additionally,advantages are found in the spatial arrangement of the detectors, thenumber of detectors 420 and in noise shielding structures of the sensor304. Disclosures pertaining thereto can also be found in the '827application, and those disclosures are also incorporated by reference intheir entirety herein.

In addition to the foregoing, the processor 402 is also configured toexecute measurement determination software instructions that usereceived detector signal data preprocessed by the front end 414 todetermine output measurement values for one or more parameters of thetissue. Exemplary algorithms for determining measurement values can befound in U.S. Pat. No. 6,157,850, U.S. patent application Ser. No.12/534,827, filed on Aug. 3, 2009 and Ser. No. 11/366,209, filed on Mar.1, 2006. The disclosure relating to determination of measurements frominput sensor data is incorporated from each of the foregoing documentsin its entirety by reference herein.

FIG. 5 illustrates an exemplary block diagram 500 of embodiments of thedriver 416 of FIG. 4. As shown in FIG. 5, the processor 402 communicateswith an address control 502 and one or more driving current controllers504 to precisely control activation of the light source 418. In anembodiment, the address control 502 outputs an address, such as, forexample, a binary number, to a decoder 506. The decoder 506 decodes theaddress and identifies particular LED(s) of the light source 418 to beconnected to the current source 504. Once connected, current flowsthrough the particular LED, thereby activating it to irradiate tissue.In an embodiment, the decoder comprises an N-to-2^(N) decoder, which anartisan will recognize from the disclosure herein to include its broadordinary meaning, including a decoder that accepts an address word, suchas, for example, a binary set of N bits, and associates that word with aparticular LED node. For example, a 4 bit word uniquely identifies 16possible LEDs. However, extension of just an additional 4 bits to an 8bit word uniquely identifies up to 256 possible LEDs or LED locations.Examples of the decoder 506 are commercially available from vendors suchas Fairchild Semiconductor, Texas Instruments, NXP Semiconductors, orthe like.

In an embodiment, the current controller 504 may comprise logic allowingthe processor 402 the ability to select from a plurality of differingcurrents levels. For example, when the light source 418 comprises, forexample, LED devices and more powerful superluminescent, laser or sideemitting LEDs, the driver 416 adjusts the current controller 504 toprovide the appropriate current to the appropriate LED at theappropriate address. For example, the current controller 504 mayadvantageously select an appropriate one of a plurality of currentsdepending on a type of LED addressed by the processor 402 through theaddress decoder 506.

In an embodiment, the current controller 504 seeks to keep currentpatterns similar regardless of whether LEDs are activated or not. Inembodiments having a plurality of different currents, twisting theconductors on which the currents travel in opposite direction to theinput data wires in the cable 306 has been shown to reduce effects ofcrosstalk on other conductors in the cable 306.

FIG. 5 also shows that the address control 502 and current controller504 may advantageously be housed in the monitor 302, although an artisanwill recognize from the disclosure herein that one or more of thecontrols 502, 504 could reside anywhere along the path from the monitor302 to the sensor 304, including the various connectors of the monitor302, the cable 306 and the sensor 304. As shown in FIG. 5, the cable 306includes conductors for the N address lines, the current sources,ground, shield, and other needs, such as, for example, conductorscommunicating with a thermister, one or more memories, or other desiredsensor devices.

FIG. 6 illustrates an exemplary flowchart of a driving process 600according to embodiment of the present disclosure. In block 601, theprocessor 402 activates the current controller to output an appropriatecurrent. In an embodiment of multiple current sources, the activationincludes a selection of an appropriate current, as will be discussedfurther with respect to FIGS. 8 and 9. In block 602, the processor 402outputs an address of a particular LED to be activated. In block 604,the N-to-2^(N) decoder 506 receives the address and determines theunique output to be activated. In an embodiment, the determinationincludes translation of a binary or other word to activation of logictransistors configured to connect a particular LED to the current sourceand in some embodiments, disconnect a short around the same LED. Inblock 606, the decoder 506 activates the appropriate logic devices toconnect the appropriate LED to the appropriate current controller 504for the duration of the determined duty cycle. In an embodiment, theaddress control 502 comprises latches set by the processor 402 in orderto control for each LED the on and off timing. In an embodiment, onenode is energized at a time, and in further embodiments, some timespacing or gap is provided between consecutive activations to guardagainst interference at the detector by light of differing wavelengths.In an embodiment, the gap, or no LED activation occurs betweenactivations of LEDs. In an embodiment, the gap comprises one of the2^(N) addressable locations such that an all-off condition isspecifically addressable by the processor 402. In an embodiment, theaddressable all-off condition may comprise multiple addresses, one foreach current level available from the current controller 504.

Although disclosed with reference to process 600, an artisan willrecognize from the disclosure herein that other processes may be used toselectively address an activation location or group of activationlocations of a light source and supply the location or group ofactivation locations with the appropriate amount of current.

FIGS. 7A and 7B illustrate exemplary block diagrams of embodiments ofthe driver 416 driving the light source 418 of FIG. 4, where the driver416 includes a single current controller. As shown in FIGS. 7A and 7B,the driver 416 includes the address control 502, the current controller504, and the decoder 506. In an embodiment, the current controller 504includes a converter 702 converting digital signals from the processorinto analog output. In an embodiment, the DAC 702 controls lightsaturation by allowing for the fine tuning of the output drive current.The DAC 702 receives clock and data signals from the processor and alatching signal dictating when the DAC should lock the data on the datasignal and stabilize the output drive current.

The output of the DAC 702 is provided to amplifier 704 which in anembodiment includes a precision voltage-to-current amplifier thatadjusts its output current based on the input voltage. The output of theamplifier 704 is also provided as the driving current to the LEDs of thelight source 418, in an embodiment, through the cable 306. A SYNC signal708 is provided to ensure precision on/off timing to the LED addressedby the decoder 506. Imperfections in the circuitry and parasiticparameters may cause the rise and fall times for the current i to beless precise than desired. The SYNC signal 708 can advantageously betimed to sink to ground some or all of the imperfections and parasiticparameters that occur during rising or falling current through the LED418 through a logic switching device 710. Sinking these imperfectionsadvantageously produces a higher quality current, which produces betteron/off activation of the light source 418, which provides for a bettersignal to noise ratio. In an embodiment, the sync signal 708 is combinedto create a single output current i. In an embodiment, the outputcurrent may comprise about 0-about 80 mA, controlled at least in part bythe voltage provided by the processor 402 to the DAC 702.

As shown in FIGS. 7A and 7B, control logic ensures that each LED of thelight source 418 can activate only when its location is decoded by thedecoder 506. For example, when a particular location is inactive, afirst logic device 712 is biased open such that current cannot flowthrough it. A second logic device 714 is biased closed to create a shortaround the LED at the inactive location; the short is also connected toground. Thus, were any parasitic current to appear on the driveconductor for the particular location, it will be simply shorted toground and cannot cause the LED to emit radiation. When the decoder 506receives the address of the particular location, the first logic device712 is biased closed and the second logic device 714 is biased open. Theclosing of device 712 connects the second logic device and the LED ofthe particular location to the current i of the current controller 504.The opening of device 714 removes the short around the LED, which is nowconnected to the drive current i, and the LED activates to emit light atits designated wavelength.

In the embodiment shown in FIG. 7A, an inverter 716 is placed at one thegates of the logic devices 712 and 714, causing them to oppose oneanother. For example, a single control signal from the decoder 504 issupplied to the gate of device 712 causing it to open or close, and itsopposite is supplied to the gate of device 714 causing it torespectively close or open. In the embodiment shown in FIG. 7B, devices712 and 714 are opposite devices such that a same signal from thedecoder 504 applied to both gates causes one of the devices 712 to openand close while the other 714 respectively closes and opens.

An artisan will recognize from the disclosure herein other logic devicesand schemes to assist in precisely governing the on/off cycles of eachLED of the light source 418 while simultaneously precisely governing thedrive current to the same.

As can also be seen in FIGS. 7A and 7B, the cable 306 carries conductorsfor the output of the current controller 504 and the address control. Inalternative embodiments, the cable 306 may also carry the SYNC signal.Thus, in various embodiments, the cable 306 may advantageously include asingle high current signal, N address signals and still be able touniquely activate substantially 2^(N) light source nodes. In anembodiment, “substantially” may be defined to be when one or more of the2^(N) light source nodes correspond to a null set where no nodes areactive. The null set is advantageous to ensure spacing between LEDactivations.

FIG. 8 illustrates another exemplary block diagram of embodiments of thedriver 416 driving the light source 418 of FIG. 4, where the driver 416comprises a plurality of current controllers 504. As shown in FIG. 8,the current controller 504 outputs two different currents i₁ and i₂ setby the voltage output by the converter 702 governed by the processor402. FIG. 8 further shows output current i₁ communicating with the nodesof a first group of LEDs, Group A, and the output current i₂communicating with the nodes of a second group of LEDs, Group B. In anembodiment, i₁ may comprise about 0-about 80 mA, while i₂ may compriseabout 0-about 800 mA. An artisan will recognize that other embodimentsmay advantageously employ other currents and/or have more or lessgroups.

Thus, in an embodiment where some of the LEDs of the light source 418comprise LEDs driven at greater power; those LEDs may advantageouslycommunicate with the output of the current source i₂. Also shown in FIG.8 is timing circuit 802 including logic configured to provideappropriate SYNC signals to logic devices 710 for sinking each ofcurrents i₁ and i₂ similar to that disclosed with reference to FIGS. 7Aand 7B.

In an embodiment, the amplifier 704 comprises a plurality of amplifiersand resistors in a feedback configuration to provide a stabilizedcurrent based on an input voltage. Such configurations are known to anartisan from the disclosure herein. In an embodiment, the timing circuit802 comprises logic combinations of signals to ensure only one of thecurrents i₁ and i₂ can flow to ground at a time. In an embodiment, theSYNC signal is logic ANDed with each of the Group A, Group B signalssuch that the SYNC and Group A signals must match to open a first logicswitch device 710 and allow current i₁ to flow, and SYNC and Group Bsignals must match to open a second logic switch device 710 and allowcurrent i₂ to flow.

FIG. 9 illustrates another exemplary block diagram of embodiments of thedriver 416 driving the light source 418 of FIG. 4, where the driver 416comprises a plurality of current controllers 504. However, in FIG. 9,the current controller 504 outputs two different currents i₁ and i₂using a single amplifier 704 and analog circuitry 902 that produces thecurrents i₁ and i₂ for Group A and Group B LEDs. Moreover, FIG. 9illustrates the SYNC signal functionality and the signal itself as partof the sensor 104. For example, in this embodiment, two locations oraddresses available on the decoder 505 correspond to the SYNC signals ofFIG. 8, such that the processor 402 produces the SYNC signals not asprocessor outputs, but as addresses of the controller 504. Timingcircuit 904 includes logic to ensure only one of the currents i₁ and i₂can flow to ground at a time by controlling logic device 710 now on thesensor 304. Thus, in the embodiment of FIG. 9, the processor 402advantageously replaces output signals with addressing. The advantagesof this embodiment include the sinking of parasitic currents andimperfections on the LED driver 416 itself, and particularly on thesensor 304, which is downstream from the cable 306. In some cases, thecable 306 produces many of the parasitic currents and imperfections dueto resistance, inductance and capacitance (or the like) associated withthe conductors and conductive materials of the cable 306. Sinking theseharmful effects downstream on the sensor ensures that they do not effectthe operation of the LEDs 418.

Although the driver circuitry is disclosed with reference to itspreferred and alternative embodiments, the disclosure is not intended tobe limited thereby. Rather, a skilled artisan will recognize from thedisclosure herein a wide number of alternatives for driver, including,for example, employing an amplifier/DAC for each group of currentcontrollers to increase performance thereof. Also, the artisan willrecognize from the disclosure herein that the address control, thedecoder, and the current controllers can individually be placed anywherealong the monitoring path. For example, the components can be housed inthe monitor 302, in the sensor 304, or in the cable 306 or connectorsassociated with any of the foregoing.

Additionally, other combinations, omissions, substitutions andmodifications will be apparent to the skilled artisan in view of thedisclosure herein. Accordingly, the present invention is not intended tobe limited by the reaction of the preferred embodiments, but is to bedefined by reference to the appended claims.

Moreover, all publications, patents, and patent applications mentionedin this specification are herein incorporated by reference to the sameextent as if each individual publication, patent, or patent applicationwas specifically and individually indicated to be incorporated byreference.

1-15. (canceled)
 16. A cable configured to communicate signals between apatient monitor and a noninvasive optical sensor, the cable comprising:one or more signal lines configured to carry one or more drive signalsto one or more optical radiation sources of the noninvasive opticalsensor; N address lines configured to carry N address signals, N beinggreater than 2; and a decoder comprising N input terminals and up to2^(N) output terminals, the decoder configured to receive the N addresssignals from the N address lines via the N input terminals and toimplement an addressing system capable of selectively individuallyaddressing 2^(N) unique outputs based on the N address signals, thedecoder configured to activate an output terminal of the up to 2^(N)output terminals based on the N address signals thereby activating theone or more optical radiation sources to provide optical radiation totissue of the patient wearing the noninvasive optical sensor andallowing one or more photodetectors of the noninvasive optical sensor todetect the optical radiation after attenuation by the tissue.
 17. Thecable of claim 16, wherein the one or more signal lines comprise atleast two signal lines configured to carry first and second drivesignals, one of the at least two signal lines configured to carry adifferent peak current level from the other of the at least two signallines.
 18. The cable of claim 17, wherein the one of the at least twosignal lines is configured to electrically connect to a first group ofthe one or more optical radiation sources, and the other of the at leasttwo signal lines is configured to electrically connect to a second groupof the one or more optical radiation sources different from the firstgroup.
 19. The cable of claim 16, wherein the one or more signal linescomprise at least two signal lines configured to carry first and seconddrive signals, and one of the at least two signal lines is configured toelectrically connect to a first group of the one or more opticalradiation sources and the other of the at least two signal lines isconfigured to electrically connect to a second group of the one or moreoptical radiation sources different from the first group.
 20. The cableof claim 16, further comprising: a first control line configured tocarry an enable signal; and a second control line configured to carry aclear signal.
 21. The cable of claim 16, further comprising: an inputconnector configured to receive the one or more drive signals and the Naddress signals from the patient monitor; an output connector configuredto provide the one or more drive signals and an activation signal fromthe activated output terminal to the noninvasive optical sensor; and aflexible conduit connecting the input connector to the output connector.22. The cable of claim 16, further comprising an output connectorconfigured to connect to the noninvasive optical sensor, the decoderbeing embedded in the output connector.
 23. The cable of claim 16,wherein the up to 2^(N) output terminals comprise 2^(N) outputterminals.
 24. The cable of claim 16, wherein the N address signalscomprise a set of N bits received in parallel.
 25. A method of operatinga noninvasive optical sensor, the method comprising: providing, by oneor more signal lines, one or more drive signals to one or more opticalradiation sources of the noninvasive optical sensor; providing, by Naddress lines, N address signals to N input terminals of a decoder, thedecoder configured to implement an addressing system capable ofselectively individually addressing 2^(N) unique outputs based on the Naddress signals, N being greater than 2; and activating an outputterminal of up to 2^(N) output terminals of the decoder based on the Naddress signals causing at least one of the one or more opticalradiation sources to transmit optical radiation to tissue of a patient,thereby allowing one or more photodetectors of the noninvasive opticalsensor to detect the optical radiation after attenuation by the tissue.26. The method of claim 25, wherein the one or more drive signalscomprise first and second drive signals, the first drive signal having adifferent peak current level from the second drive signal.
 27. Themethod of claim 26, further comprising providing the first drive signalto a first group of the one or more optical radiation sourceselectrically connected to one of the one or more signal lines andproviding the second drive signal to a second group of the one or moreoptical radiation sources electrically connected to the other of the oneor more signal lines, the second group being different from the firstgroup.
 28. The method of claim 25, wherein the one or more drive signalscomprise first and second drive signals, and further comprisingproviding the first drive signal to a first group of the one or moreoptical radiation sources electrically connected to one of the one ormore signal lines and providing the second drive signal to a secondgroup of the one or more optical radiation sources electricallyconnected to the other of the one or more signal lines, the second groupbeing different from the first group.
 29. The method of claim 25,further comprising: providing, by a first control line, an enable signalto the decoder; and providing, by a second control line, a clear signalto the decoder.
 30. The method of claim 25, further comprising:receiving, by an input connector, the one or more drive signals and theN address signals from the patient monitor; and providing, by an outputconnector, the one or more drive signals and an activation signal fromthe activated output terminal to the noninvasive optical sensor.
 31. Themethod of claim 25, wherein the up to 2^(N) output terminals comprise2^(N) output terminals.
 32. The method of claim 25, wherein the Naddress signals comprise a set of N bits received in parallel.
 33. Apatient monitor configured to communicate with a noninvasive opticalsensor, the patient monitor comprising: a processor configured to selecta desired wavelength of optical radiation emitted by one or more opticalradiation sources of the noninvasive optical sensor; a current controlcircuit configured to supply a current to the one or more opticalradiation sources; and an address control circuit configured to set awavelength of the optical radiation emitted by the one or more opticalradiation sources to the desired wavelength by outputting an address of2^(N) addresses as a set of N bits transmitted separately via N outputterminals, each of at least some of the 2^(N) addresses uniquelycorresponding to a different wavelength of the optical radiation emittedby the one or more optical radiation sources, N being greater than 2.34. The patient monitor of claim 33, wherein the current control circuitis configured to supply a level of the current depending at least on theoutput address.
 35. The patient monitor of claim 33, further comprisingan input configured to receive an output signal from the noninvasiveoptical sensor in response to the address control circuit outputting theaddress, the output signal indicative of one or more physiologicalconditions of a patient being monitored and responsive to the opticalradiation with the desired wavelength detected after attenuation by bodytissue of the patient at a measurement site.